PEP 498: Formatted string literals

Formatted string literals are prefixed with 'f' and are similar to the format strings accepted by str.format(). They contain replacement fields surrounded by curly braces. The replacement fields are expressions, which are evaluated at run time, and then formatted using the format() protocol:

>>> name = "Fred">>> f"He said his name is {name}."'He said his name is Fred.'>>> width = 10>>> precision = 4>>> value = decimal.Decimal("12.34567")
>>> f"result: {value:{width}.{precision}}"# nested fields'result: 12.35'